System and method for reproducible manufacturing of electrode for secondary battery

ABSTRACT

A system for manufacturing an electrode for a secondary battery is disclosed herein. In an embodiment, the system for manufacturing the electrode for the secondary battery comprises a supply roller for supplying a collector having a long sheet shape; an electrode active material coating device for applying an electrode active material to a surface of the collector supplied by the supply roller to manufacture an unfinished electrode; a rolling roller for rolling a surface of the unfinished electrode and adjusting a thickness of the electrode active material to manufacture a finished electrode; and an electrode quality inspection device for inspecting quality of the electrode through a surface roughness value of the rolling roller, a surface roughness value of the surface of the electrode, and a rolling load value of the rolling roller.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a divisional of U.S. application Ser. No.16/467,177, filed on Jun. 6, 2019, which is a national phase entry under35 U.S.C. § 371 of International Application No. PCT/KR2018/007314,filed on Jun. 27, 2018, which claims priority from Korean PatentApplication No. 10-2017-0092289, filed on Jul. 20, 2017, the disclosuresof which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a system and method for manufacturingan electrode for a secondary battery, and more particularly, to a systemand method manufacturing an electrode for a secondary battery, whichinspect quality of the electrode through a surface roughness and alinear pressure (rolling load) of a rolling roller and a surfaceroughness of the electrode.

BACKGROUND ART

In general, secondary batteries refer to chargeable and dischargeablebatteries, unlike primary batteries that are not chargeable. Thesecondary batteries are being widely used in the high-tech electronicfields such as mobile phones, notebook computers, and camcorders.

Such a secondary battery is classified into a can type secondary batteryin which an electrode assembly is built in a metal can and a pouch typesecondary battery in which an electrode assembly is built in a pouch.The pouch type secondary battery comprises an electrode assembly, anelectrolyte, and a pouch accommodating the electrode assembly and theelectrolyte. Also, the electrode assembly has a structure in which aplurality of electrodes and a plurality of separators are alternatelystacked.

The electrode comprises a collector and an electrode active materialapplied to a surface of the collector. A method for manufacturing theelectrode comprises a step of supplying a collector, a step of applyingan electrode active material to a surface of the collector tomanufacture an unfinished electrode, and a step of rolling theunfinished electrode by using a rolling roller to manufacture a finishedelectrode.

However, in the method for manufacturing the electrode, as the rollingprocess of the electrode is repeated, a surface roughness of the rollingroller gradually increases. When the electrode is rolled by using therolling roller of which the surface roughness increases, a surfaceroughness of the electrode may be deteriorated to continuously produceabnormal electrodes.

DISCLOSURE OF THE INVENTION Technical Problem

The present invention has been made to solve the above-describedproblems, and an object of the present invention is to provide a systemand method for manufacturing an electrode for a secondary battery, inwhich quality of the electrode is inspected through a surface roughnessand a linear pressure (rolling load) of a rolling roller for rolling theelectrode and a surface roughness of the rolled electrode to preventabnormal electrodes from being produced, and in particular to accuratelyconfirm replacement of the rolling roller.

Technical Solution

To achieve the above-described object, a system for manufacturing anelectrode for a secondary battery according to an embodiment of thepresent invention comprises: a supply roller supplying a collectorhaving a long sheet shape; an electrode active material coating deviceapplying an electrode active material to a surface of the collectorsupplied by the supply roller to manufacture an unfinished electrode; arolling roller rolling a surface of the unfinished electrode andadjusting a thickness of the electrode active material to manufacture afinished electrode; and an electrode quality inspection devicecomprising a rolling roller measuring unit measuring surface roughnessof the rolling roller, an electrode measuring unit measuring a surfaceroughness of the electrode active material applied to the finishedelectrode, a pressure measuring unit measuring a rolling load appliedfrom the rolling roller to the unfinished electrode, and an inspectionunit performing a first inspection for determining whether the surfaceroughness value of the rolling roller, which is measured by the rollingroller measuring unit, is within a range of an inputted surfaceroughness value of the rolling roller, performing a second inspectionfor determining whether a surface roughness value of the finishedelectrode, which is measured by the electrode measuring unit, is withina range of an inputted surface roughness of the electrode, andperforming a third inspection for determining whether a pressure loadvalue of the rolling roller, which is measured by the pressure measuringunit, is within a range of an inputted rolling load value.

The electrode quality inspection device may determine the finishedelectrode as a normal product when all of the results are determined asbeing normal through the first to third inspections, determine thefinished electrode as a product to be re-inspected when one or tworesults are determined as being normal, and the rest result isdetermined as being abnormal through the first to third inspections, anddetermine the finished electrode as an abnormal product when all of theresults are determined as being abnormal through the first to thirdinspections.

The electrode quality inspection device may have an inspection period inwhich the first, second, and third inspections are performed atintervals of 2 weeks to 4 weeks.

The electrode quality inspection device may re-inspect the surfaceroughness of the rolling roller or the electrode and the rolling load ofthe rolling roller, which are determined as being abnormal, when one ortwo results are determined as being normal, and the rest result isdetermined as being abnormal through the first to third inspections.

The electrode quality inspection device may stop an operation of therolling roller when the surface roughness of the rolling roller or theelectrode and the rolling load of the rolling roller, which aredetermined as being abnormal, are determined as being abnormal evenafter the re-inspection.

The electrode quality inspection device may change the inspection periodof 2 weeks to 4 weeks, at which the first to third inspections areperformed, into an inspection period of 2 days to 7 days when thesurface roughness of the rolling roller or the electrode and the rollingload of the rolling roller, which are determined as being abnormal, aredetermined as being normal through the re-inspection.

The electrode quality inspection device may stop an operation of therolling roller when all of the results are determined as being abnormalthrough the first to third inspections.

The rolling roller measuring unit may comprise a roughness testermeasuring the surface roughness while contacting the surface of therolling roller, and in the roughness tester, a tip having a needleshape, which is attached to one surface, may measure roughness whilemoving from a surface of one end to a surface of the other end of therolling roller and calculate a mean value of a maximum mountain heightand a minimum mountain height within a moving distance to calculate thesurface roughness value of the rolling roller.

The roughness tester may measure the surface roughness at at least fourspots in a circumferential direction of the rolling roller.

The inputted surface roughness value of the rolling roller may range of0.5 μm or less.

The electrode measuring unit may comprise an optical measuring partmeasuring surface roughness while enlarging and photographing thesurface of the finished electrode, and

the optical measuring part may enlarge and photograph the surface of thefinished electrode while moving from one end to the other end in a widthdirection of the finished electrode and calculates a maximum mountainheight and a minimum mountain height within the moving distance tocalculate the surface roughness value of the finished electrode.

The inputted surface roughness value of the rolling roller may be 3 μmor less.

The pressure measuring unit may comprise a pressure sensor, and thepressure sensor may measure the rolling load applied to the unfinishedelectrode through the rolling roller to calculate the rolling loadvalue.

The inputted rolling load value of the rolling roller may be 1.5 kg/m²to 2.0 kg/m².

A method for manufacturing an electrode for a secondary batteryaccording to an embodiment of the present invention comprises: a supplystep (S10) of supplying a collector having a long sheet shape; anelectrode active material coating step (S20) of applying an electrodeactive material to a surface of the collector to manufacture anunfinished electrode; an electrode manufacturing step (S30) of rolling asurface of the unfinished electrode by using a rolling roller andadjusting a thickness of the electrode active material to manufacture afinished electrode; and an electrode quality inspection step (S40)comprising a first process (S41) of measuring a surface roughness valueof the rolling roller, a second process (S42) of measuring a surfaceroughness value of the electrode active material applied to the finishedelectrode, a third process (S43) of measuring a rolling load appliedfrom the rolling roller to the electrode, a fourth process (S44) ofperforming a first inspection to determine whether the measured surfaceroughness value of the rolling roller is within a range of the inputtedsurface roughness value of the rolling roller, a fifth process (S45) ofperforming a second inspection to determine whether the measured surfaceroughness value of the finished electrode is within a range of theinputted surface roughness value of the electrode, and a sixth process(S46) of performing a third inspection to determine whether the rollingload value of the rolling roller is within a range of the inputtedrolling load value of the rolling roller.

In the electrode quality inspection step (40), the finished electrodemay be determined as a normal product when all of the results aredetermined as being normal through the first to third inspections,determined as a product to be re-inspected when one or two results aredetermined as being normal, and the rest result is determined as beingabnormal through the first to third inspections, and determined as anabnormal product when all of the results are determined as beingabnormal through the first to third inspections.

ADVANTAGEOUS EFFECTS

The present invention has effects as follows.

First: The system for manufacturing the electrode for the secondarybattery may comprise the electrode quality inspection device comprisingthe rolling roller measuring part, the pressure measuring part, theelectrode measuring part, and the inspection part. Due to theabove-described structural features, the abnormal electrodes may beprevented from being produced, and in particular, the replacement timeof the rolling roller may be accurately confirmed.

Second: In the system for manufacturing the electrode for the secondarybattery, if all of the surface roughness of the rolling roller, thesurface roughness of the electrode active material, and the rolling loadvalue of the rolling roller are normal, it may be determined as thenormal product.

If any one or two are abnormal, it may be determined as a re-inspectionproduct, and if all of them are abnormal, it may be determined as theabnormal product. Due to the above-described features, the electrode maybe more finely divided according to the quality thereof, and inparticular, the quality inspection of the electrode may be improved inaccuracy.

Third: The system for manufacturing the electrode for the secondarybattery may have the inspection period to inspect the surface roughnessand the rolling load of the rolling roller and the surface roughness ofthe electrode at intervals of 2 weeks to 4 weeks. Due to theabove-described features, the quality inspection of the electrode may bestably performed within the range that does not significantlydeteriorate the productivity of the electrode.

Fourth: In the system for manufacturing the electrode for the secondarybattery, if the electrode is determined as the product to bere-inspected, the surface roughness of the rolling roller, the surfaceroughness of the electrode, and the rolling load of the rolling roller,which are inspected as abnormal, may be re-inspected. Due to theabove-described features, the abnormal inspection due to the measurementerror may be prevented, and thus, the quality inspection of theelectrode may be significantly improved in accuracy.

Fifth: In the system for manufacturing the electrode for the secondarybattery, if the surface roughness of the rolling roller, the surfaceroughness of the electrode, and the rolling load of the rolling rollerare re-inspected and then determined as being normal, the inspectionperiod may be shortened to 2 day to 7 day at intervals of 2 weeks to 4weeks. Thus, the timing of occurrence of the abnormal electrode may bemore precisely and quickly confirmed.

Sixth: in the system for manufacturing the electrode for the secondarybattery, if all of the surface roughness of the rolling roller, thesurface roughness of the electrode, and the rolling load of the rollingroller are determined as being abnormal, the operation of the rollingroller may be stopped. Due to the above-described features, the abnormalelectrodes may be prevented from being produced. Particularly, thereplacement time of the rolling roller may be precisely predictedthrough the quality inspection for the electrode, and thus, the rollingroller that is determined as being abnormal may be replaced and mountedto perform the process of manufacturing the electrode again.

Seventh: The system for manufacturing the electrode for the secondarybattery according to the present invention may inspect the surfaceroughness of the rolling roller through the roughness tester. Due to theabove-described features, the surface roughness value of the rollingroller may be more precisely inspected.

Eighth: The system for manufacturing the electrode for the secondarybattery according to the present invention may inspect the surfaceroughness value of the electrode active material unit applied to theelectrode through the optical measuring part. Due to the above-describedfeatures, the surface roughness value of the electrode active materialunit may be more precisely inspected.

Ninth: The system for manufacturing the electrode for the secondarybattery according to the present invention may measure the rolling loadapplied from the rolling roller to the electrode through the pressuresensor. Due to the above-described features, the rolling load value ofthe rolling roller may be more precisely inspected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of a system for manufacturing an electrode for asecondary battery according to an embodiment of the present invention.

FIG. 2 is a perspective view illustrating a rolling roller measuringportion of a device for inspecting quality of the electrode according toan embodiment of the present invention.

FIG. 3 is an inspection chart illustrating results obtained through thesystem for manufacturing the electrode for the secondary batteryaccording to an embodiment of the present invention.

FIG. 4A is a photograph of the surface roughness of an electrode from afirst experimental example showing a measurement state of a surfaceroughness of the electrode according to an embodiment of the presentinvention

FIG. 4B is a graph of a surface roughness value of the electrode fromthe first experimental example.

FIG. 5A is a photograph of the surface roughness of an electrode from asecond experimental example showing a measurement state of a surfaceroughness of the electrode according to an embodiment of the presentinvention

FIG. 5B is a graph of a surface roughness value of the electrode fromthe second experimental example.

FIG. 6 is a graph illustrating a time-varying linear pressure (a rollingload) of the rolling roller according to an embodiment of the presentinvention.

FIG. 7 is a flowchart illustrating a method for manufacturing anelectrode for a secondary battery according to an embodiment of thepresent invention.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings in such a manner thatthe technical idea of the present invention may easily be carried out bya person with ordinary skill in the art to which the invention pertains.The present invention may, however, be embodied in different forms andshould not be construed as limited to the embodiments set forth herein.In the drawings, anything unnecessary for describing the presentinvention will be omitted for clarity, and also like reference numeralsin the drawings denote like elements.

[System for Manufacturing Electrode for Secondary Battery According toEmbodiment]

As illustrated in FIG. 1 , a system for manufacturing an electrode for asecondary battery according to an embodiment of the present inventioncomprises a supply roller 110 supplying a collector 11 having a longsheet shape, an electrode active material coating device 120 applying anelectrode active material 12 to a surface of the collector 11 suppliedby the supply roller 110 to manufacture an unfinished electrode 10 a, arolling roller 130 rolling a surface of the unfinished electrode 10 aand adjusting a thickness of the electrode active material 12 tomanufacture a finished electrode 10, and an electrode quality inspectiondevice 140 inspecting quality of the finished electrode 10 through asurface roughness of the rolling roller 130, a rolling load of therolling roller 130, and a surface roughness of the finished electrode 10passing through the rolling roller 130.

The collector 11 having the long sheet shape is wound around the supplyroller 110. When the supply roller 110 rotates, the wound collector 11having the long sheet shape is supplied to the electrode active materialcoating device 120.

The electrode active material coating device 120 comprises a storageunit in which the electrode active material 12 is stored and aninjection nozzle injecting the electrode active material 12 stored inthe storage unit into a surface of the collector 11. That is, theelectrode active material coating device 120 may apply the electrodeactive material 12 onto the surface of the collector 11 to manufacturethe unfinished electrode 10 a.

The rolling roller 130 may be provided in a pair to roll top and bottomsurfaces of the unfinished electrode 10 a at the same time and adjust athickness of the electrode active material 12 of the unfinishedelectrode 10 a, thereby manufacturing the finished electrode 10.

The surface roughness on the surface of the rolling roller 130 may besignificantly deteriorated by stretches occurring while rolling theunfinished electrode 10 a. When the unfinished electrode 10 a is rolledby using the rolling roller 130 of which the surface roughness isdeteriorated, the surface roughness of the unfinished electrode 10 a maybe significantly deteriorated to deteriorate battery performance andthereby to produce an abnormal electrode.

Also, the surface roughness of the unfinished electrode 10 a may bedeteriorated due to a difference in rolling load applied from therolling roller 130 to the unfinished electrode 10 a.

To solve above problems, the present invention comprises an electrodequality inspection device 140 for performing a quality inspection of theelectrode through the surface roughness and the rolling load of therolling roller 130 and the surface roughness of the finished electrode10. Particularly, the electrode quality inspection device 140 mayinspect the quality of the finished electrode 10 and also more preciselyconfirm a replacement time of the rolling roller 130 of which thesurface roughness is deteriorated.

That is, the electrode quality inspection device 140 comprises a rollingroller measuring unit 141 measuring the surface roughness of the rollingroller 130, an electrode measuring unit 142 measuring the surfaceroughness of the electrode active material 12 applied to the finishedelectrode 10, a pressure measuring unit 143 measuring the rolling loadapplied from the rolling roller 130 to the unfinished electrode 10 a,and an inspection unit 144 inspecting quality of the finished electrode10 on the basis of a surface roughness value Rz of the rolling roller130, which is measured by the rolling roller measuring unit 141, asurface roughness value Rz of the finished electrode 10, which ismeasured by the electrode measuring unit 142, and a rolling load valueof the rolling roller 130, which is measured by the pressure measuringunit 143.

Referring to FIGS. 1 and 2 , the rolling roller measuring unit 141comprises a roughness tester measuring the surface roughness whilecontacting the surface of the rolling roller 130. In the roughnesstester, a tip having a needle shape, which is attached to one surface,measures roughness while moving from a surface of one end to a surfaceof the other end of the rolling roller 130 and then calculates a meanvalue of a maximum mountain height and a minimum mountain height withinthe moving distance and thereby to calculate the surface roughness valueRz of the rolling roller 130.

For example, as illustrated in FIG. 2 , the roughness tester measuresroughness while moving along points indicated in a longitudinaldirection of the rolling roller 130 and calculates a mean value of themeasured roughness values, thereby calculating the surface roughnessvalue Rz of the rolling roller 130.

Particularly, the roughness tester may measure surface roughness at atleast four spots in a circumferential direction of the rolling roller130 and calculate a mean value of the surface roughness, which aremeasured at the at least four spots, to calculate a surface roughnessvalue Rz of the rolling roller 130, thereby more precisely calculatingthe surface roughness value Rz of the rolling roller 130.

The electrode measuring unit 142 comprises an optical measuring partmeasuring surface roughness while enlarging and photographing a surfaceof the finished electrode 10. The optical measuring part may enlarge andphotograph the surface of the finished electrode 10 while moving fromone end to the other end in a width direction of the finished electrode10 and then calculate a maximum mountain height and a minimum mountainheight within the moving distance to calculate the surface roughnessvalue Rz of the finished electrode 10. Particularly, the opticalmeasuring part may measure surface roughness at at least four spots inthe width direction of the finished electrode 10 and calculate a meanvalue of the surface roughness, which are measured at the at least fourspots, to calculate a surface roughness value Rz of the finishedelectrode 10, thereby more precisely calculating the surface roughnessvalue Rz of the rolling roller 10.

For example, as illustrated in FIGS. 4A and 5A, the optical measuringpart enlarges and photographs the surface of the finished electrode 10.Also, the optical measuring part moves from one side to the other sideof the enlarged and photographed picture. Here, the heights of themountains within the moving distance are displayed in a waveform on amonitor. Here, the surface roughness value Rz of the rolling roller,which is measured by the rolling roller measuring unit 141 may bedisplayed on the monitor, and the surface roughness value Rz of thefinished electrode 10, which is measured by the optical measuring part,which is disposed below the rolling roller measuring unit 141. Thus, thesurface roughness of the rolling roller 130 and the finished electrode10 may be confirmed at once.

First Experimental Example

As a first experimental example, referring to FIGS. 4A and 4B, theelectrode measuring unit 142 displays 0.4 μm that is a surface roughnessvalue Rz of the rolling roller, which is measured by the rolling rollermeasuring unit 141, on a monitor 20 (see FIG. 4B). Next, the electrodemeasuring unit 142 enlarges and photographs a surface of the finishedelectrode 10 (see FIG. 4A). Next, the electrode measuring unit 142displays a mountain height (or roughness) on the monitor 20 in awaveform 21 while moving from one side to the other side of the enlargedand photographed picture, and a mean value of a maximum height and aminimum height of the displayed waveform is calculated to calculate thesurface roughness value Rz of the finished electrode 10. Here, referringto the waveform of FIG. 4B, the surface roughness value Rz of thefinished electrode 10 is calculated to 0.45 μm, and 0.45 μm that is thecalculated surface roughness value Rz of the finished electrode 10 isdisplayed on the monitor 20.

Thus, when the unfinished electrode 10 a is rolled by using the rollingroller 130 having a surface roughness value Rz of 0.4 μm, the finishedelectrode having 0.45 μm of the surface roughness value Rz may bemanufactured.

Second Experimental Example

As a second experimental example, referring to FIGS. 5A and 5B, theelectrode measuring unit 142 displays 1.0 μm that is a surface roughnessvalue Rz of the rolling roller, which is measured by the rolling rollermeasuring unit 141, on a monitor 20 (see FIG. 5B). Next, the electrodemeasuring unit 142 enlarges and photographs a surface of the finishedelectrode 10 (see FIG. 5A). Next, the electrode measuring unit 142displays a mountain height (or roughness) on the monitor 20 in awaveform 21 while moving from one side to the other side of the enlargedand photographed picture, and a mean value of a maximum height and aminimum height of the displayed waveform is calculated to calculate 0.66μm that is a surface roughness value Rz of the finished electrode 10.Then, 0.66 μm that is the calculated surface roughness value Rz of thefinished electrode 10 is displayed on the monitor 20.

Thus, when the unfinished electrode 10 a is rolled by using the rollingroller 130 having a surface roughness value Rz of 1.0 μm, the finishedelectrode having 0.66 μm of the surface roughness value Rz may bemanufactured.

Third Experimental Example

As a third experimental example, the first experimental example and thesecond experimental example are performed on five unfinished electrodes10 a, and the results may be summarized as shown in the table of FIG. 3. That is, a mean surface roughness value of the rolling roller 130 anda mean surface roughness value Rz of the finished electrode 10 may becalculated, and a quality inspection of the finished electrode 10 andwhether or not the rolling roller is replaced may be inspected throughthe mean surface roughness value of the rolling roller 130 and the meansurface roughness value Rz of the finished electrode 10.

The pressure measuring unit 143 may comprise a pressure sensor measuringa rolling load applied from the rolling roller 130 to the unfinishedelectrode 10 a. The pressure sensor measures a rolling load applied tothe unfinished electrode 10 a through the rolling roller 130 tocalculate a rolling load value. For example, the pressure sensor isinstalled between the rolling roller 130 and the unfinished electrode 10a to detect a variation in load applied while the unfinished electrode10 a is rolled by the rolling roller 130, thereby calculating a rollingload value of the rolling roller 130.

The inspection unit 144 performs a first inspection on the basis of thesurface roughness value Rz of the rolling roller 130, which iscalculated by the rolling roller measuring unit 141, performs a secondinspection on the basis of the surface roughness value Rz of thefinished electrode 10, which is calculated by the electrode measuringunit 142, and performs a third inspection to determine whether therolling load value of the rolling roller, which is measured by thepressure measuring unit 143, is within a range of the inputted rollingload value of the rolling roller, thereby precisely inspecting thequality of the finished electrode 10.

For example, the inspection unit 144 performs a first inspection fordetermining whether the surface roughness value Rz of the rolling roller130, which is measured by the rolling roller measuring unit 141, iswithin a range of the inputted surface roughness value Rz of the rollingroller, performs a second inspection for determining whether the surfaceroughness value Rz of the finished electrode 10, which is measured bythe electrode measuring unit 142, is within a range of the inputtedsurface roughness of the electrode, and performs a third inspection fordetermining whether the pressure load value of the rolling roller, whichis measured by the pressure measuring unit 143, is within a range of theinputted rolling load value.

Also, the inspection unit 144 may determine the finished electrode 10 asa normal product when all of the results are determined as being normalthrough the first, second, and third inspections. Also, when one or tworesults are determined as being normal, and the rest result isdetermined as being abnormal through the first, second, and thirdinspections, the finished electrode 10 is determined as a product to bere-inspected. Also, the inspection unit 144 may determine the finishedelectrode 10 as an abnormal product when all of the results aredetermined as being abnormal through the first, second and thirdinspections.

Here, the inspection unit 144 recognizes that there is no problem in thesurface roughness of the rolling roller 130 and the surface roughness ofthe finished electrode 10 when the finished electrode 10 is determinedas the normal product. Thus, the inspection period of the surfaceroughness of the rolling roller 130 and the surface roughness of thefinished electrode 10 may be set long to improve efficiency of the work.For example, the inspection unit 144 has an inspection period forinspecting the surface roughness of the rolling roller 130 and theelectrode 10 at intervals of 2 weeks to 4 weeks.

The inspection unit 144 re-inspects the surface roughness of the rollingroller 130 or the surface roughness of the finished electrode 10 whenone or two results are determined as being normal, and the rest resultis determined as being abnormal through the first, second, and thirdinspections. For example, the inspection unit 144 may determine that ameasurement error occurs when the result is determined as being abnormalthrough the first inspection, and the results are determined as beingnormal through the second and third inspections, or when the results aredetermined as being normal through the first and second inspections, andthe result is determined as being abnormal through the third inspection.Thus, the surface roughness and the rolling load of the rolling roller130 and the surface roughness of the finished electrode 10, which aredetermined as being abnormal, may be re-inspected to prevent abnormalinspection due to the measurement error from occurring, therebyimproving accuracy of the inspection.

Here, the inspection unit stops the operation of the rolling roller 130so that the abnormal electrode is continuously manufactured when thesurface roughness and the rolling load of the rolling roller 130 and thesurface roughness of the finished electrode 10, which are determined asbeing abnormal, are determined as being abnormal even after there-inspection. Also, the abnormal rolling roller may be replaced with anew rolling roller to perform the electrode manufacturing process again.Thus, the replacement period of the rolling roller 130 may be accuratelyconfirmed.

When the surface roughness and the rolling load of the rolling rollerand the surface roughness of the electrode, which are determined asbeing abnormal, are determined as normal after the re-inspection, thefinished electrode 10 that is the re-inspected product may be determinedas the normal product. Also, the inspection unit 144 may change theinspection period to a shorter period because the occurrence of theabnormal rolling roller 130 is likely to occur again. For example, theinspection period of the inspection unit 144 is changed from a period of2 weeks to 4 weeks to a period of 2 days to 7 days. Thus, the occurrencetime of the abnormal rolling roller 130 or finished electrode 10 may bemore accurately and quickly confirmed.

The range of the inputted surface roughness value Rz of the rollingroller 130 may be 0.5 μm or less, preferably, 0.4 μm or less. That is,when the range of the inputted surface roughness value Rz of the rollingroller 130 is 0.5 μm or more, the surface roughness of the finishedelectrode 10 may be significantly deteriorated to deteriorateperformance. Thus, the range of the inputted surface roughness value Rzof the rolling roller 130 may be 0.5 μm or less, preferably, 0.4 μm orless to prevent the quality of the electrode from being deteriorated.

The inputted surface roughness value Rz of the electrode may be 3 μm orless, preferably, 2 μm or less. That is, when the inputted surfaceroughness value Rz of the electrode is 3 μm or more, there is a problemthat the performance of the finished electrode is significantlydeteriorated. Thus, the inputted surface roughness value Rz of theelectrode may be 3 μm or less, preferably, 2 μm or less to prevent thequality of the electrode from being deteriorated.

The range of the inputted rolling load value of the rolling roller 130may be 1.5 kg/m² to 2.0 kg/m². That is, when the range of the inputtedrolling load value of the rolling roller 130 is 1.5 kg/m² or less, thereis a problem that the finished electrode 10 a is not effectively rolled.

When the range of the inputted rolling load value of the rolling roller130 is 2.0 kg/m² or more, the unfinished electrode 10 a may be stronglyrolled, and thus, it may be difficult to accurately adjust a thickness.Particularly, frictional force between the rolling roller 130 and theunfinished electrode 10 a may significantly increase to greatly causethe surface roughness.

Fourth Experimental Example

As a fourth experimental example, the test results of the variation inload applied from the rolling roller 130 to the unfinished electrode 10a may be summarized as shown in the graph of FIG. 6 . That is, it isseen that the value of the rolling load applied from the rolling roller130 to the unfinished electrode 10 a gradually increases from 1.9 kg/m²to 2.4 kg/m² as a time elapses. Thus, as the time elapses, the surfaceroughness of the rolling roller 130 increases. As a result, it is seenthat the increase in surface roughness of the rolling roller 130 causesan increase in rolling load value of the rolling roller 130.

The above-described system for manufacturing the electrode for thesecondary battery according to an embodiment of the present inventionmay inspect the surface roughness and the rolling load of the rollingroller 130 and the surface roughness of the finished electrode 10 at thesame time. Due to the above-described feature, the quality inspection ofthe electrode may be more precisely performed. Particularly, thereplacement period of the rolling roller for rolling the electrode maybe more accurately determined.

Hereinafter, a manufacturing method using the system for manufacturingthe electrode for the secondary battery according to an embodiment ofthe present invention will be described.

[Method for Manufacturing Electrode for Secondary Battery According toEmbodiment]

As illustrated in FIG. 7 , the method for manufacturing an electrode fora secondary battery according to an embodiment of the present inventioncomprises a supply step (S10) of supplying a collector 11 having a longsheet shape, an electrode active material coating step (S20) of applyingan electrode active material 12 to a surface of the collector 11 tomanufacture an unfinished electrode 10 a, an electrode manufacturingstep (S30) of rolling a surface of the unfinished electrode 10 a byusing a rolling roller 130 and adjusting a thickness of the electrodeactive material 12 to manufacture a finished electrode 10, and anelectrode quality inspection step (S40) of inspecting quality of thefinished electrode 10 through a surface roughness value Rz of therolling roller 130, a rolling load value of the rolling roller 130, anda surface roughness value Rz of the electrode active material 12 appliedto the finished electrode 10.

In the supply step (S10), the collector 11 having the long sheet shape,which is wound around a supply roller 110, is continuously supplied toan electrode active material coating device 120.

In the electrode active material coating step (S20), the electrodeactive material 12 may be applied to the surface of the collector 11supplied by the supply roller 110 through the electrode active materialcoating device 120 to manufacture the unfinished electrode 10 a.

In the electrode manufacturing step (S30), the unfinished electrode 10 amay be rolled by using the rolling roller 130 to uniformly adjust thethickness of the electrode active material 12, thereby manufacturing thefinished electrode 10.

The electrode quality inspection step (S40) is performed to inspectquality of the finished electrode 10. The electrode quality inspectionstep (S40) comprises a first process (S41) of measuring a surfaceroughness value Rz of the rolling roller 130, a second process (S42) ofmeasuring a surface roughness value Rz of the electrode active materialapplied to the finished electrode 10, a third process (S43) of measuringa rolling load applied from the rolling roller 130 to the electrode, afourth process (S44) of performing a first inspection to determinewhether the measured surface roughness value Rz of the rolling roller130 is within a range of the inputted surface roughness value Rz of therolling roller, a fifth process (S45) of performing a second inspectionto determine whether the measured surface roughness value Rz of thefinished electrode 10 is within a range of the inputted surfaceroughness value Rz of the electrode, and a sixth process (S46) ofperforming a third inspection to determine whether the rolling loadvalue of the rolling roller 130 is within a range of the inputtedrolling load value of the rolling roller.

In the first process (S41), the surface roughness of the rolling roller130 is measured through a rolling roller measuring unit 141. That is, inthe rolling roller measuring unit 141 a tip having a needle shape, whichis attached to one surface, measures roughness while moving from asurface of one end to a surface of the other end of the rolling roller130 and then calculates a mean value of a maximum mountain height and aminimum mountain height within the moving distance and thereby tocalculate the surface roughness value Rz of the rolling roller 130.

In the second process (S42), the surface roughness of the electrodeactive material 12 applied to the finished electrode 10 is measuredthrough an electrode measuring unit 142. That is, the electrodemeasuring unit 142 enlarges and photographs a surface of the finishedelectrode 10 and calculates a maximum mountain height and a minimummountain height within a moving distance while moving from one end tothe other end of the photographed image to calculate the surfaceroughness value Rz of the electrode.

In the third process (S43), the rolling load applied from the rollingroller 130 to the unfinished electrode 10a is measured through apressure measuring unit 143. That is, the input measuring unit 143detects a variation in load applied while the unfinished electrode 10 ais rolled by the rolling roller 130 to calculate the rolling load valueof the rolling roller 130.

In the fourth process (S44), the inspection unit 144 performs the firstinspection to determine whether the surface roughness value Rz of therolling roller 130, which is measured by the rolling roller measuringunit 141, is within a range of the inputted surface roughness value Rzof the rolling roller.

For example, the inspection unit 144 determines the measured surfaceroughness value Rz of the rolling roller 130 as being normal when therange of the inputted surface roughness value Rz of the rolling rolleris 0.5 μm or less, preferably, 0.4 μm or less, and the surface roughnessvalue Rz of the rolling roller, which is measured by the rolling rollermeasuring unit 141, is 0.4 μm. If the surface roughness value Rz of therolling roller 130, which is measured by the rolling roller measuringunit 141, is 0.7 μm, the measured surface roughness value Rz of therolling roller 130 is determined as being abnormal.

In the fifth process (S45), the inspection unit 144 performs the secondinspection to determine whether the surface roughness value Rz of thefinished electrode 10, which is measured by the electrode measuring unit142, is within a range of the inputted surface roughness value Rz of theelectrode.

For example, the inspection unit 144 determines the measured surfaceroughness value Rz of the finished electrode 10 as being normal when therange of the inputted surface roughness value Rz of the electrode is 3μm or less, preferably, 2 μm or less, and the measured surface roughnessvalue Rz of the finished electrode is 2 μm. If the measured surfaceroughness value Rz of the finished electrode 10 is 4 μm, the measuredsurface roughness value Rz of the finished electrode 10 is determined asbeing abnormal.

In the sixth process (S46), the inspection unit 144 performs the thirdinspection to determine whether the rolling load value of the rollingroller 130, which is measured by the rolling roller measuring unit 143,is within a range of the inputted rolling load value of the rollingroller.

For example, the inspection unit 144 determines the measured rollingload value of the rolling roller as being normal when the range of theinputted rolling load value is 1.5 kg/m² to 2.0 kg/m², and the measuredrolling load value of the rolling roller 130 is 1.9 kg/m².

Here, in the electrode quality inspection step (S40), the finishedelectrode 10 is determined as the normal product when all of the resultsare determined as being normal through the first, second, and thirdinspections. Also, the finished electrode 10 is determined as theproduct to be re-inspected when one or two results are determined asbeing normal, and the rest result is determined as being abnormalthrough the first, second, and third inspections. Also, the finishedelectrode 10 is determined as the abnormal product when all of theresults are determined as being abnormal through the first, second andthird inspections.

Thus, in the method for manufacturing the electrode for the secondarybattery according to an embodiment of the present invention, the qualityof the finished electrode may be more precisely inspected.

Accordingly, the scope of the present invention is defined by theappended claims rather than the foregoing description and the exemplaryembodiments described therein. Various modifications made within themeaning of an equivalent of the claims of the invention and within theclaims are to be regarded to be in the scope of the present invention.

1. A method for manufacturing an electrode for a secondary battery, themethod comprising: supplying a collector having a long sheet shape;applying an electrode active material to a surface of the collector tomanufacture an unfinished electrode; rolling a surface of the unfinishedelectrode by using a rolling roller and adjusting a thickness of theelectrode active material to manufacture a finished electrode; measuringa surface roughness value of the rolling roller and determining, in afirst inspection, whether the measured surface roughness value of therolling roller is within a range of inputted surface roughness value ofthe rolling roller; measuring a surface roughness value of the electrodeactive material applied to the finished electrode and determining, in asecond inspection, whether the measured surface roughness value of thefinished electrode is within a range of inputted surface roughness valueof the electrode; and measuring a rolling load applied from the rollingroller to the electrode and determining, in a third inspection, whetherthe rolling load value of the rolling roller is within a range ofinputted rolling load value of the rolling roller.
 2. The method ofclaim 1, wherein the finished electrode is determined as a normalproduct, a product to be re-inspected, or an abnormal product, whereinthe finished product is a normal product when the measured surfaceroughness value of the surface roller, the measured surface roughnessvalue of the electrode, and the measured rolling load value are withinthe respective ranges of the the first to third inspections, wherein thefinished product is a product to be re-inspected when one or two of themeasured surface roughness value of the surface roller, the measuredsurface roughness value of the electrode, and the measured rolling loadvalue are within the respective ranges of the first to thirdinspections, and the remaining measured values are outside therespective ranges of the first to third inspections, and wherein thefinished product is an abnormal product when all of the measured surfaceroughness value of the surface roller, the measured surface roughnessvalue of the electrode, and the measured rolling load value are withinthe respective ranges of the first to third inspections.